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BUG: KCSAN: data-race in filemap_read / generic_write_end

write to 0xffff88810ad67808 of 8 bytes by task 4708 on cpu 0:
 i_size_write include/linux/fs.h:886 [inline]
 generic_write_end+0xb1/0x350 fs/buffer.c:2168
 ext4_da_write_end+0x26c/0x620 fs/ext4/inode.c:3096
 generic_perform_write+0x264/0x3f0 mm/filemap.c:3764
 ext4_buffered_write_iter+0x235/0x3e0 fs/ext4/file.c:285
 ext4_file_write_iter+0x2c7/0x1170
 call_write_iter include/linux/fs.h:2191 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88810ad67808 of 8 bytes by task 4709 on cpu 1:
 i_size_read include/linux/fs.h:864 [inline]
 filemap_read+0xfb5/0x1510 mm/filemap.c:2687
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2821
 ext4_file_read_iter+0x1c8/0x280
 call_read_iter include/linux/fs.h:2185 [inline]
 generic_file_splice_read+0xde/0x2b0 fs/splice.c:309
 do_splice_to fs/splice.c:793 [inline]
 splice_direct_to_actor+0x26c/0x620 fs/splice.c:865
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000c4d000 -> 0x0000000000c4e000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4709 Comm: syz-executor.3 Not tainted 6.1.0-rc3-syzkaller-00332-g089d1c31224e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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